Refrigeration apparatus and method having control for refrigeration effect and condenser heat rejection



March 17, 970 R. v. ANDERSON. 3,500,653 REFRIGERATION APPARATUS AND METHOD HAVING CONTROL FOR REFRIGERATION EFFECT AND CONDENSER HEAT REJECTION Filed April 5. 1968 INVENTOR Robe/'2 V. Anderson BY g A ORNEY3- United States Patent US. Cl. 62-117 14 Claims ABSTRACT OF THE DISCLOSURE An expansion-compression, continuous cycle cooling system in which the enthalpy of the working medium at certain zones of both the high and the low pressure sides of the circuit is controlled in a manner to maintain the heat rejection of the condenser and the refrigeration effect of the evaporator in proper balance.

The improvements of my present invention are predicated on the principle that development of the most eflicient and economical refrigeration cycle necessitates recognition of the fact that there is a direct and important relationship between the heat gain at a low temperature by the evaporator, the heat gain resulting from mechanical work done by the compressor, and removal by the condenser at a higher temperature of the total heat thus absorbed by the refrigerant. Coefficient of Performance (removal of the greatest amount of heat for the least expenditure of mechanical work) is an important aspect of the instant invention.

It is, therefore, one important object of this invention to control condenser heat rejection so that it will not exceed the total of the heat of compression and the heat gain by the evaporator.

Another important object of the instant invention is to control the heat gained by the evaporator from its load as a function of the designed temperature difference between the substance being cooled and the desired evaporator minimum temperature.

Still another important object of the present invention is to provide control means which will protect the compressor against damage, though operating continually, by preventing entrapment or starvation of lubricating oil, and by precluding the flow of liquid refrigerant thereto.

A further important object of my present invention is to provide means for controlling the enthalpy of the refrigerant in the high pressure side of the circuit between the condenser and the expansion device by use of a bypass for feeding high temperature gas from the compressor into the liquid emanating from the condenser, together with valving which alternately opens and closes the outlets of the condenser and the bypass, the valving being actuated by a temperature sensitive device in heat transfer relationship to the refrigerant whose enthalpy is being controlled.

A still further important object of the present invention is to control the enthalpy of the fluid at the inlet and the outlet of the evaporator by the combination of a pair of valve units and a heat exchanger, with one unit constantly supplying a fluid of proper enthalpy to one side of the heat exchanger and with the other unit providing controlled flow of fluid to the other side of the heat exchanger, as well as to the evaporator, so as to accomplish, among other things, protection of the compressor, conice trolled condenser heat rejection, and preselected evaporator temperature range, as aforesaid.

In the drawing, the single figure is a schematic representation of cooling apparatus having means for controlling refrigeration effect and condenser heat rejection in accordance with my present invention. Compressor 10, condenser 12, expansion device 14 and evaporator 16 are coupled in a continuous refrigeration cycle as illustrated. The refrigerant emanating from compressor is fed to the inlet of condenser 12 by a line 18 to which is connected a conduit 20 for directing the working medium to chamber 22 of a valve unit 24, bypassing the condenser 12. Unit 24 includes a pair of valves 26 and 28 on a common rod 30 adapted to alternately close the outlet of conduit 20 into chamber 22 and the outlet of condenser 12 into chamber 22 respectively. Expansion and contraction of a bellows 32 within chamber 22 reciprocates rod 30 within guide 34 to open or close valves 26 and 28.

Another valve unit 36 has a bellows 38 within section 40a of its compartment 40 operable upon expansion and contraction to reciprocate a rod 42 in guide 44 and alternately open or close a pair of valves 46 and 48 located in section 40b of compartment 40. A perforated partition 50 in compartment 40 surrounds rod 42 and cooperates with valve 46 when the latter is closed to separate sections 40a and 40b, thereby blocking the flow of the refrigerant from the evaporator coil 16. It is to be understood, however, that the details of construction of the units 24 and 36, either as thus described or as shown in the drawing, are for illustrative purposes only.

A heat exchanger 52 has a coil 54 within its hollow body 56, the coil 54 being interposed in line 58 which connects chamber 22 with device 14. Line 60 between device 14 and evaporator '16 is coupled with passage means 62 for directing the medium to section 40b of compartment 40 through body 56, bypassing evaporator 16. Flow from device 14 through body 56 is blocked when valve 48 closes the outlet of passage 62. A line 64 couples section 4012 of compartment 40 with the inlet of compressor 10.

The interiors of the bellows 32 and 38 may be charged with a substance that is normally solid, such as wax or a mixture of waxes selected from one or more petroleum derivatives, capable of changing state to a liquid upon absorption of a predetermined quantity of heat. Or, they may be charged with a substance that is normally liquid, selected from those which have a coefficient of expansion high enough in the liquid state to provide suflicient bellows movement within the desired temperature range to close the corresponding valves alternately. Moreover, a limited fill, wherein part of the fluid is in liquid phase and part in vapor phase when both valves are open would be satisfactory in view of the fact that the controls, in each instance, are temperature sensitive, i.e., dependent upon the heat content of the substances within the bellows, to in turn control the enthalpy of the refrigerant in both the high and in the low pressure sides of the circuit.

For the above reasons the bellows 32, or other temperature responsive control device, must be within the refrigerant flowing to the expansion valve 14, as shown (ahead of coil 54 when heat exchanger 52 is used) or otherwise in heat exchange relationship to such refrigerant at that zone in order to control valves 26 and 28. 'Similarly, the bellows 38, or other heat responsive control, must be within the refrigerant at the outlet of evaporator 16, as shown, or in heat exchange relationship thereto in order to control valves 46 and 48, because each control is, as aforesaid, temperature responsive only and not dependent upon or sensitive to pressure changes in the refrigerant, i.e., each :ontrol must be under the influence of heat at all times.

The operating temperatures of valve units 24 and 36 may be selected from a wide range in accordance with desired refrigerating duty or amount of cooling. effect to be produced by the system, which is in turn subject to wide variations, both through diversity of design and diversity of operating conditions to which the same machine is often subjected. Therefore, neither the nature nor the physical and chemical properties of the fills for the bellows 32 and 38 can be defined within any critical limits.

For a full understanding of my invention, it must be recognized that if valves 28 and 46 are closed, no external work is performed. Compressor merely circulates the refrigerant continuously from line 18 through conduit 20, past valve 26 into chamber 22, into line 58, through coil 54 and expansion device 14, into passage 62 through body 56, into section 40b of compartment 40 past valve 48, and thence back to compressor 10 via line 64, with no resultant refrigerating effect, and with no damage to the compressor 10 because no liquid will enter its inlet from line 64.

On the other hand, in a conventional circuit, with units 24 and 36 and heat exchanger 52 omitted, compressor 10 must operate at a variable speed if the heat loss from condenser 12 is to be equal to or less than the heat gain by evaporator 16 plus the heat of compression so as to prevent fiow of liquid to compressor 10 from line 64. If the compressor 10 in such conventional circuit operates at a constant speed, then the heat gain by evaporator 16 must be equal to or greater than the heat loss by condenser 12 in order to supply compressor 10 with liquid-free vapor from line 64.

However, in an automobile air conditioner, for example, the system frequently operates in a highly unbalanced condition. The speed of the compressor varies directly with the speed of the engine crankshaft and the condenser heat rejection is a function of the engine fan speed as well as the ram air cooling effect through the condenser, which varies with changes in speeds of forward motion. Thus, with the evaporator cooling load in the automobile substantially constant, the balanced condition cannot exist at all. times.

In most commercial refrigeration systems and air conditioning units the compressor speed is constant. Some type of thermostatic device is oftentimes used to stop the compressor when the coolingload is satisfied to protect the compressor against liquid refrigerant entering its inlet. Suih devices do not, however, protect the compressor if the condenser heat loss is greater than the heat gain by the evaporator prior to actuation of the thermostat. This necessitates the use of a thermostatically controlled expansion valve to supply the compressor with only a gas of some preselected value of superheat from the evaporator.

;;;Accordingly, in my invention, selection of the temperature of the refrigerant supply to the coil 54 determines the filLto be chosen for bellows 32. According to my inventionalso, selection of the temperature of the refrigerant at the outlet of evaporator 16 determines the fill to be chosen for bellows 38. Thus, the valve unit 24 operates tdisupply a fluid of constant high temperature, whose enthalpy can never be lower than saturated liquid at 100 Flfto one side (coil 54) of the heat exchanger 52, and valve unit'36 provides control of the flow of low temperature fluid through evaporator 16 and/or the other side (body 56) of heat exchanger 52, because body 56 is connected in parallel with evaporator 16.

Thus having described the various elements of the systern as shown in the drawing, the following is an example of the events and conditions occurring within a refrigeration system using my novel method and apparatus:

For the unit 24- and unit 36 there are three possible valve positions for each unit. Therefore, there. arg six possible va p s o s in th y em. These are:

Position #1-valve 26 closed, valve 28 open in unit 24. Position #2--valve 26 open, valve 28 open in unit 24. Position #3valve 26 open, valve 28 closed in unit 24. Position #4-valve 48 closed, valve 46 open in unit 36. Position #5valve 48 open, valve 46 open in unit 36. Position #6valve 48 open, valve 46 closed in unit 36.

Assigning values to the positions for purposes of illustration in this example the positions are as follows:

Position #1-Valve 26 will be closed and valve 28 will be open whenever the temperature of the liquid from the condenser 12 through valve 28 to chamber 22 is equal to or above 110 F. Thus, position #1 results from any combination of conditions within the system, or external to the condenser 12 or evaporator 16, which causes the liquified refrigerant from condenser 12 to have a temperature above 110 F. As long as this liquid temperature remains at or above 110 F., the wax within the bellows 32 will remain expanded to keep valve 26 closed.

Position #2Valves 26 and 28 will be open whenever the temperature of the liquid from the condenser 12 to valve 28 is below 110 F. and above F. Thus, position #2 occurs when the temperature of the liquified refrigerant from the condenser 12, due to any combination of 'events within the system, or external to the condenser 12 or evaporator 16, which causes the temperature of the liquid flowing to chamber 22 to be below F.; the bellows 32 will contract sufiiciently to cause unit 24 to maintain position #2.

The fluid in conduit 20, admitted to chamber 22 through valve 26, is superheated vapor directly from the compressor 10. Therefore, on occurrence of position #2, only a'small quantity of the superheated vapor is admixed with the low temperature (below 110 F.) condenser liquid, which, because of the exchange of enthalpy between the superheated vapor and the liquid, will cause the temperature of the liquid in chamber 22 to rise, resulting in the desired expansion effect on the bellows 32 to return the valves 26 and 28 in unit 24 to position #1.

For any combination of events within the system or external to the condenser 12 which cause position #2 to occur, the rejection of heat by the condenser 12 is limited. The extent of the limitation of the condenser heat rejection is determined by whatever proportion of the. high enthalpy superheated vapor is used for mixing in chamber 22 with condenser liquid to maintain the fluid temperature around bellows 32 above 100 F. and below 110 F. When total use of the high enthalpy of the superheated vapor from conduit 20 results in a fluid temperature in the chamber 22 below 100 F. the contracting action of the bellows 32 will keep the valve 28 closed, which are the conditions described in position #3.

Position #3Valve 26 is open and valve 28 is closed whenever the temperature of the vapor from conduit 20 through valve 26 is below 100 F. This event is possible only when the enthalpy of the vapor in line 64 is such that when the heat of compression is added the temperature of the vapor from the compressor 10 through conduit 20 and valve 26 is below 100 F. When valve 28 is closed the condenser 12 can reject no more heat because there is no further flow of refrigerant through it. The condenser 12 now becomes a reservoir, storing to its internal capacity, highly sub-cooled liquid refrigerant.

Position #4Valve 48 is closed and valve 46 is open whenever the temperature of the superheated vapor at the outlet of the evaporator 16, caused by heat gain from its cooling load, is above 42 F. This causes expansion (liquefaction of the Wax) in the bellows 38 which closes valve 48, Thus, the fluid within the evaporator 16 is a saturated liquid-vapor mixture at its inlet, saturated vapor at its midpoint and superheated vapor at its outlet. The enthalpy of the vapor at the outlet of the evaporator 16 is high at the operating pressure and temperature maintained within evaporator 16 by the compressor 10. All heat gained by the evaporator refrigerant, with unit 36 in position #4, is from the external cooling l a and superheated vapor is supplied to compartment 40 and to line 64 thereby.

Position #5Valves 46 and 48 will be open whenever the temperature of the superheated vapor at the outlet of evaporator 16 is below 42 F. and above 28 F. This is caused by insufiicient heat gain by the refrigerant from the evaporator cooling load to produce a temperature above 42 F. in the superheated vapor at the outlet of evaporator 16. Since the temperature of the superheated vapor at the outlet of evaporator 16 is lower than 42 F the wax within bellows 38 will contract (partially solidify) to open valve 48. When 48 is opened, the parallel circuit (passage 62 and body 56 to compartment 40 and to evaporator 16) is opened. The pressure of the supply from expansion device 14 is equal at the inlets of the line 60 and the passage 62. The length of the line 60 through evaporator 16 to section 40b is much longer than the length of the parallel circuit comprising passage 62 and body 56 to section 40b. The flow resistance through line 60 is greater than the flow resistance through passage 62; therefore, the supply from expansion device 14, instantaneously seeking the path of least flow resistance, flows through the parallel circuit (passage 62 and body 56). Flow through this parallel circuit will continue until the pressure in the compartment 40 is raised to the corresponding smaller pressure drop through the parallel circuit. This means that the outlet pressure of the evaporator 16 is raised. Therefore, only heat now gained from the cooling load can drive saturated vapor from the evaporator 16 into section 40b. As the compressor draws vapor from section 40b, the parallel circuit tries to remain the path of least flow resistance and supply the needs of the compressor 10. But the heat continually added to the evaporator 16 by its cooling load generates saturated vapor, the volume of which raises the evaporator pressure very slightly to overcome the instantaneous higher pressure created in section 40b and force the thus produced saturated vapor in the section 40b to mix with the flow from the parallel circuit. Thus, the cooling effect of the evaporator 16 on its cooling load is limited to its ability to create saturated vapor from the cooling load.

The designed temperature dilference between body 56 and coil 54 is greater than the temperature dilference between the evaporator 16 and its cooling load, with an evaporator outlet vapor temperature less than 42 F. Therefore, the enthalpy and pressure of the vapor, highly superheated from passage 62 through valve 48 to the section 40b, is greater than the enthalpy and pressure of the saturated vapor from section 40a. Thus, there is no longer any superheated vapor from the evaporator outlet, only saturated vapor. The enthalpy of the vapor from the section 40b to line 64 is at or slightly above its enthalpy value previous to the opening of valve 48. Thus, the compressor 10 is assured of always receiving superheated vapor from the section 40b.

When flow occurs through the parallel circuit (passage 62 and body 56) the temperature and enthalpy of the liquid in the line 58 ahead of the expansion device 14 is lowered by the vaporization of the low pressure fluid from the expansion device 14. Thus, the lower enthalpy liquid, upon passing through the expansion device 14, requires a smaller portion of the flow to vaporize (flash gas) so to cool the remaining liquid to the saturation conditions of saturated liquid at the pressure-temperature conditions maintained in the evaporators (evaporator 16 and the parallel circuit), by the compressor 10. Thus the refrigeration effect of each pound of refrigerant circulated by the compressor 10 is increased, without any increase in the input energy required to drive the compressor 10, refrigeration efiect being defined as the difference between the enthalpy of the vapor leaving an evaporator and the enthalpy of the liquid approaching an expansion device.

In all successful refrigeration systems, the selection of the compressor and evaporator capacities must always be equal to or greater than the maximum cooling load imposed on the system. Thus, it is necessary standard practice to select a compressor and evaporator which will have excess capacity at all cooling load conditions other than maximum design limit. Therefore, in the instant example, the capacity of the evaporator 16 will be greater than the normal cooling load imposed thereon. As a consequence thereof the temperature and enthalpy of the saturated vapor will descend, causing further contraction of the bellows 38, with further improvement of the refrigeration effect of each pound of refrigerant circulated by the compressor 10 (because of the parallel circuit) to the point that the temperature of the saturated vapor will reach 28 F. and valve 46 will close. However, valve 46 will remain closed only as long as the vapor from evaporator 16 is below 28 F., i.e. the cooling load is below 28 F.

From the point of opening of the valve 48 to the closing of the valve 46, the power input to drive the compressor 10 is reduced in direct ratio to the increase in refrigeration eflFect because any flow through the parallel circuit is an internal exchange of heat and conservation of energy, requiring no real work to be performed. This is analogous to the energy that is stored by condensers and induction coils in electrical circuits where the only real work is done by current flowing through an electrical resistance. In my invention the coil 54 (like an inductance coil in an electrical circuit) lags the rate of change of enthalpy in the evaporator, while the body 56 (like an electrical condenser) leads the rate of change of enthalpy in the evaporator 16. Thus the flow through the heat exchanger 52 requires no real work to be done by the compressor 10. The only real work done by the compressor 10 is that required to keep the vapor pressure within the evaporator 16 low enough for heat exchange to occur between the low pressure refrigerant and the cooling load. Therefore, the evaporator 16 is like an electrical resistance.

Position #6Valve 48 is open and valve 46 is closed whenever the temperature of the saturated Vapor in section 40a is at or below 28 F. This event is possible only when the cooling load of evaporator 16 is removed completely, such as when the evaporator fan in an air conditioning unit is turned off, or when the temperature of the cooling load is 28 F. or less. The evaporator 16 will become a reservoir, storing saturated liquid to its internal capacity after having absorbed all of the latent heat of the saturated vapor within it that was previously supplied to the vapor by the cooling load. The evaporator 16 will remain in this state waiting for the opportunity to absorb heat from any outside source and will have its maximum capacity for heat absorption.

The flow through the parallel circuit will continue to improve the refrigeration effect of the refrigerant and provide a constant supply of superheated vapor to line 64 because of heat exchanger 52. The heat exchanger circuit will provide a continuous path for the compressor 10 to circulate the remaining small amount of refrigerant and lubricating oil at the minimum input energy to drive the compressor 10.

Having described all possible valve positions in the system, the following is a description of all possible combinations of conditions of the above valve positions in an air cooled air conditioning unit:

Condition #1-Combination of position #1 and position #4.

Condition #2-Combination of position #1 and position #5.

Condition #3-Combination of position #1 and position #6.

Condition #4-Combination of position #2 and position #4.

Condition #5-Combination of position #2 and position #5.

Condition #6-Combination of position #2 and posiion #6.

Condition #7--Combination of position #3 and posiion #4.

Condition #8-Combination of position #3 and posiion #5.

Condition #9Combination of position #3 and posiion.#6.

Condition #1 (valves 26 and 48 closed; valves 28 and I6 open) will occur during normal operation of the unit vith high condenser ambient, high evaporator cooling oad, maximum compressor input energy, and minimum efrigeration effect.

Condition #2 (valve 26 closed; valves 28, 46 and 48 pen) will occur during normal operation of the unit with high condenser ambient, average evaporator cooling oad, lower compressor input energy and higher refrigeraion effect (inverse ratio between input energy and re Erigeration effect) Condition #3 (valves 26 and 46 closed; valves 28 and 18 open) is extremely rare and for all practical purposes mpossible to sustain. It requires high condenser ambimt, no evaporator cooling load, maximum refrigeration affect and minimum compressor input energy.

Condition #4 (valve 48 closed, valves 26, 28 and 46 open) will occur in normal operation with moderate to 2001 condenser ambient, high evaporator cooling load, average refrigeration effect and average compressor input energy.

Condition #5 (all four valves open) will occur in normal operation with moderate to cool condenser ambient, average evaporator cooling load, improved refrigeration effect and compressor input energy in inverse ratio to the improvement in refrigeration effect.

Condition #6 (valve 46 closed; valves 26, 28 and 48 open) is rare and for all practical purposes impossible to sustain. It requires moderate to cool condenser ambient, no evaporator cooling load, maximum refrigeration effect and minimum compressor input energy. 7

Condition #7 (valves 26 and 46 open; valves 28 and 48 closed) is extremely rare and for all practical purposes impossible to sustain. It requires very cold condenser ambient, high evaporator cooling load, average to minimum refrigeration effect and average compressor input energy.

Condition #8 (valve 28 closed; valves 26, 46 and 48 open) is extremely rare and for all practical purposes impossible to sustain. It requires very cold condenser ambient, average evaporator cooling load, average to good refrigeration effect, average to low compressor input energy.

Condition #9 (valves 26 and 48 open; valves 28 and 46 closed) will occur in normal operation, if compressor 10 is required to operate continuously with very cold condenser ambient, no evaporator cooling load, maximum refrigeration effect and minimum compressor input energy. In this condition most of the refrigerant in the system is stored in the condenser 12 and the evaporator 16. The remaining refrigerant is circulated by compressor 10 through coil 54, which acts as a condenser, and through body 56, which acts as an evaporator. Thus. the vapor from the compressor 10 is condensed in coil 54. The liquid from coil 54 is supplied to expansion device 14, then to passage 62, and then to the body 56 where it is evaporated and superheated and returned to the compressor 10. Since all flow is confined to the heat exchanger 52, no work is performed and the exchange of internal enthalpy means minimum compressor energy input.

None of the above conditions will result in damage to the system or to its components. Conditions 1, 2, 4 and 5 are encountered with the greatest frequency when the unit is needed.

In summary then, when the heat from the substance being cooled by evaporator 16 is sufiicient to cause total vaporization of all refrigerant being supplied from device 14, and such that the temperature of the superheated vapor in secion a is above 42 F., valve 48 will close and all gas flowing from evaporaor 16 to compressor 10 will be superheated.

The highly superheated vapor flowing into section 40b will raise the pressure in compartment 40, thereby raising the pressure at the outlet of evaporator 16, retarding flow fom evaporaor 16 to section 40a. The refrigerant which continues to flow through evaporator 16 receives heat from the substance being cooled and from the superheated vapor within evaporator 16. Thus, the improved quality liquid flowing from device 14 to evaporator 16 converts the superheat and a portion of the latent heat of vaporization (previously supplied by the substance being cooled) to an improved quality refrigerant in evaporator 16, capable of maximum heat extraction from the substance because of the low enthalpy of such refrigerant. While this action causes no temperature change of the refrigerant in evaporator 16, an enormous quantity of heat is nevertheless exchanged. Then, when enough heat is absorbed from the substance around evaporator 16 to cause saturated vapor to flow to section 40a so as to raise the temperature therein to 42 F., valve 48 will close.

From the foregoing, it is manifest that a number of advantageous results are attained: (a) improved quality refrigerant supply from expansion device 14, i.e., minimum flash gas with a liquid condition having a sufficiently low heat content to assure adequate refrigeration effect in evaporator 16 to meet the requirements of the heat load; (b) maintenance of a balanced condition by virtue of automatic multiple valve unit operations whenever the condenser coolant is such that the heat rejection by condenser 12 is excessive or inadequate in relation to refrigeration effect in evaporator 16, or conversely, whenever the heat load is such that the refrigeration effect is excessive or inadequate in relation to heat rejection; (c) supply of liquid-free vapor to compressor 10 at all times. It is necessary also not to overlook the important function of heat exchanger 52 because it is the exchange of heat between the refrigerant in coil 54 and in body 56, operating in conjunction with the units 24 and 36, that makes possible the novel results above explained. Having thus described the invention, what is claimed as new and desired to be secured by letters Pa ent is:

1. A process of cooling in a continuous cycle which comprises the steps of:

exerting sufiicient pressure on a superheated refrigerant to cause it to liquefy when cooled;

lowering the temperature of a first portion of the superheated, high pressure refrigerant sufficiently to liquefy the same;

directing a second portion of the superheated, high pressure refrigerant for flow into the high pressure, liquefied refrigerant to raise the enthalpy of the latter;

restricting the flow of said high pressure, liquefied refrigerant and thereupon decreasing the pressure thereof;

directing a first portion of the decreased pressure refrigerant into heat exchange relationship with a substance to be cooled;

directing a second portion of the decreased pressure refrigerant into heat exchange relationship to the high pressure, liquefied refrigerant to raise the temperature of said second portion of decreased pressure refrigerant;

directing said second portion of high temperature, de-

creased pressure refrigerant for flow into said first portion of decreased pressure refrigerant to raise the enthalpy of the latter prior to again increasing the pressure thereof in continuation of the cycle; and blocking the flow of said second portion of the superheated, high pressure refrigerant into the high pressure, liquefied refrigerant when the latter rises to a predetermined enthalpy.

2. A process of cooling as set forth in claim 1; and

blocking the flow of said high pressure, liquefied refrigerant into said second portion of superheated, high pressure refrigerant when the high pressure, liquefied refrigerant falls to a second predetermined enthalpy lower than said first mentioned predetermined enthalpy.

3. A process of cooling as set forth in claim 2; and

blocking the flow of said first portion of decreased pressure refrigerant into said second portion of high temperature, decreased pressure refrigerant when said first portion of decreased pressure refrigerant when said first portion of decreased pressure refrigerant falls to a preselected enthalpy.

4. A process of cooling as set forth in claim 2; and

blocking the flow of said second portion of high temperature, decreased pressure refrigerant into said first portion of decreased pressure refrigerant when the latter rises to a preselected enthalpy.

5. A process of cooling as set forth in claim 3; and

blocking the flow of said second portion of high temperature, decreased pressure refrigerant into said first portion of decreased pressure refrigerant when the latter rises to a second preselected enthalpy higher than said first mentioned preselcted enthalpy.

6. A process of cooling as set forth in claim 1; and

blocking the fiow of said first portion of decreased pressure refrigerant into said second portion of high temperature, decreased pressure refrigerant when said first portion of decreased pressure refrigerant falls to a preselected enthalpy.

7. A process of cooling as set forth in claim 6; and

blocking the flow of said second portion of high temerature, decreased pressure refrigerant into said first portion of decreased pressure refrigerant when the latter rises to a second preselected enthalpy higher than said first mentioned preselected enthalpy.

8. A process of cooling as set forth in claim 1; and

blocking the flow of said second portion of high temperature, decreased pressure refrigerant into said first portion of decreased pressure refrigerant when the latter rises to a preselected enthalpy.

9. A process of cooling in a continuous cycle which comprises the steps of:

exerting suificient pressure on a superheated refrigerant to cause it to liquefy when cooled;

lowering the temperature of a first portion of the superheated, high pressure refrigerant sufficiently to liquefy the same;

directing a second portion of the superheated, high pressure refrigerant for flow into the high pressure, liquefied refrigerant to raise the enthalpy of the latter;

blocking the flow of said second portion of the superheated, high pressure refrigerant into the high pressure, liquefied refrigerant when the latter rises to a predetermined enthalpy;

restricting the flow of said high pressure, liquefied refrigerant and thereupon decreasing the pressure thereof; and

directing the decreased pressure refrigerant into heat exchange relationship with a substance to be cooled prior to again pressurizing the same in continuation of the cycle, and

blocking the flow of said high pressure, liquefied refrigerant into said second portion of superheated, high pressure refrigerant when the high pressure, liquefied refrigerant falls to a second predetermined enthalpy lower than said first mentioned predetermined enthalpy.

10. A process of cooling in a continuous cycle which comprises the steps of:

exerting sufficient pressure on a superheated refrigerant to cause it to liquefy when cooled; lowering the temperature of a first portion of the superheated, high pressure refrigerant sufiiciently to liquefy the same; directing a second portion of the superheated, high pressure refrigerant for fiow into the high pressure, liquefied refrigerant to raise the enthalpy of the latter; blocking the flow of said second portion of the superheated, high pressure refrigerant into the high pressure, liquefied refrigerant when the latter rises to a predetermined enthalpy; restricting the flow of said high pressure, liquefied refrigerant and thereupon decreasing the pressure thereof; and directing the decreased pressure refrigerant into heat exchange relationship with a substance to be cooled prior to again pressurizing the same in continuation of the cycle, and blocking the flow of said first portion of decreased pressure refrigerant into said second portion of high temperature, decreased pressure refrigerant When said first portion of decreased pressure refrigerant falls to a preselected enthalpy. 11. A process of cooling as set forth in claim 9; and blocking the flow of said first portion of decreased pressure refrigerant into said second portion of high temperature, decreased pressure refrigerant when said first portion of decreased pressure refrigerant falls to a preselected enthalpy. 12. A process of cooling in a continuous cycle which comprises the steps of:

exerting sufiicient pressure on a superheated refrigerant to cause it to liquefy when cooled; lowering the temperature of the superheated, high pressure refrigerant sufiiciently to liquefy the same; restricting the flow of said high pressure, liquefied refrigerant and thereupon decreasing the pressure thereof; directing a first portion of the decreased pressure refrlgerant into heat exchange relationship with a substance to be cooled; directing a second portion of the decreased pressure refrigerant into heat exchange relationship to the high pressure, liquefied refrigerant to raise the temperature of said second portion of decreased pressure refrigerant; directing said second portion of high temperature, de-

creased pressure refrigerant for flow into said first portion of decreased pressure refrigerant to raise the temperature of the latter prior to again increasing the pressure thereof in continuation of the cycle; and blocking the flow of said first portion of decreased pressure refrigerant into said second portion of high temperature, decreased pressure refrigerant when said first portion of decreased pressure refrigerant falls to a preselected enthalpy. 13. A process of cooling as set forth in claim 12; and blocking the flow of said second portion of high temperature, decreased pressure refrigerant into said first portion of decreased pressure refrigerant when the latter rises to a second preselected enthalpy higher than said first mentioned preselected enthalpy. 14. A process of cooling in a continuous cycle which comprises the steps of:

exerting sufiicient pressure on a superheated refrigerant to cause it to liquefy when cooled; lowering the temperature of the superheated, high pressure refrigerant sufliciently to liquefy the same; restricting the flow of said high pressure, liquefied refrigerant and thereupon decreasing the pressure thereof; directing a first portion of the decreased pressure refrigerant into heat exchange relationship with a substance to be cooled;

directing a second portion of the decreased pressure refrigerant into heat exchange relationship to the high pressure, liquefied refrigerant to raise the temperature of said second portion of decreased pressure refrigerant;

directing said second portion of high temperature, decreased pressure refrigerant for flow into said first portion of decreased pressure refrigerant to raise the temperature of the latter prior to again increasing the pressure thereof in continuation of the cycle; and

blocking the flow of said second portion of high temperature, decreased pressure refrigerant into said first 12 portion of decreased pressure refrigerant when the latter rises to a preselected enthalpy.

References Cited UNITED STATES PATENTS 3,210,955 10/1965 Anderson et al. 62--l17 3,368,364 2/1968 Norton et a1 '62117 LLOYD L. KING, Primary Examiner U.S. Cl. X.R. 

